Cyclic Loads and Fatigue Analysis of Steel Structures of Frame Mine Headframes

Abstract

The structures of mine headframes are classified as lifting and transport mining structures, which fall under the highest responsibility class. Most mine headframes in Ukraine have been in operation for extended periods, subjected to intense cyclic dynamic loads and aggressive environmental conditions. Consequently, there is a need to assess the residual life of these structures and ensure they meet the required service life in terms of fatigue strength. Currently, fatigue analysis for mine headframe structures is not covered by existing standards, as there is no established methodology for determining typical load cycles. Based on an analysis of the key stages in the technological cycle of mine hoisting installations, it is proposed to define a typical load cycle as the sequential application of loads from two design scenarios: the design scenario of the maximum total tension force in the hoisting rope branches, and the design scenario of the minimum total force in the hoisting rope branches. These scenarios, combined with constant and long-term loads, define the maximum and minimum stresses in the load cycle for the critical sections of the structures. This methodology accounts for dynamic forces arising from forced oscillations of the lifting vessels when calculating the cyclic forces in the hoisting ropes. For the characteristic structure, the types of structural elements and critical sections for endurance analysis are identified in accordance with the provisions of the standard methodology. Through the analysis of the stress-strain state in the critical sections of the mine headframe structure, the characteristics of dynamic stress cycles were determined, and a fatigue strength calculation was performed. The analysis revealed a limited fatigue life for the main beams of the headframe structure. The proposed engineering method for analyzing the fatigue strength of mine headframe structures can be applied both in the design of new structures and in the development of systems for monitoring the technical condition of operating mine headframes.